Hi all, I'd like to design an RF transmitter receiver system that can control say 8 relays. I found something on the net that I want to build myself in the following site: http://www.apogeekits.com/rf_remote_control_set.htm Some people told me about some transmitter/encoder IC's like HT12E and one built in LINX KH RXD http://www.linxtechnologies.com/Products/RF-Modules What is the theory of operation of these encoders? I'd like someone to explain very briefly the theory of operation and the tranmission type of this digital data and modulation types too ... and if you can refer me to more resources. I haven't read about digital communications for a long time. Just mention very brief description or topics names and I can find myself more explanations. Do these encoders use ASK (Amplitude Shift Keying)? Also, someone told me to use DTMF circuits. Can I get the same results using these circuits and what are the differences? And I think I can control 2^8 devices through these circuits if I used DECODERS in the receiver circuit, right? Thank you very much :)